In microelectronic cooling systems, Indium has traditionally been used as a solder thermal interface material to thermally attach microelectronic devices such as integrated circuits (IC) to heat spreading devices. Because of recent surges in Indium demand, the raw Indium price has skyrocketed in recent years (e.g., as of April 2006, Indium price ˜$1,000/kg) severely increasing the cost of Indium used in IC packaging.
Although Indium's low melting temperature (156° C.) and thermal conductivity (K=82 W/m·K) make it suitable for solder attachment in IC packaging, Indium's low melting point also creates reliability challenges when, for example, Indium-soldered joints are subjected to temperature cycling. Moreover, Indium typically forms intermetallic compounds with other metals near attached surfaces causing microcracks. Intermetallic compounds may serve as void nucleation sites during hydrostatic stress driven voiding, weakening the structural integrity of the soldered joint. Solutions that incorporate more cost-effective thermal interface materials and/or intermetallic compound-free joints while providing high thermal conductivity are needed in the IC packaging industry to reduce such microcracking and temperature cycle reliability problems.